Predictive factors of cytotoxic damage in radioactive iodine treatment of differentiated thyroid cancer patients.

Radioactive iodine (131I) therapy in patients suffering from differentiated thyroid cancer (DTC) is a targeted treatment commonly used for thyroid ablation and locoregional and distant metastatic spread management. Despite a significant proportion of the 131I dose entering the circulation, there is currently no detailed information regarding its effect on the blood cell system. In order to assess the cytotoxic effects of 131I therapy on the circulatory system, blood cell levels, thyroid-related hormones and CD45+ cell cytotoxicity were estimated in blood collected from patients with DTC. The micronuclei (MN) frequency of the peripheral blood CD45+ cell fraction was significantly increased after 30 days of 131I therapy compared to that prior to treatment, although a strong individual variation was observed. A significantly negative correlation between MN frequency and the level of platelets and plateletcrit was observed; however, there was no such correlation with thyroid-related hormones. These resultS suggest that the correlation between MN frequency and the platelet system may serve as a biomarker of exposure and, possibly, of sensitivity in DTC patients undergoing 131I therapy following thyroid and lymph node surgery.